I don't know a whole lot about this issue. While I was at Liberty, Stuart over the summer, I saw them bubble test a number of coaches for leaking panels.
I didn't think about this much until I read this thread and ran into a Prevost Maintenance Bulletin (Mi97-24). It is an 8-page PDF which describes using the evaporator motor, powered by a 24v charger-battery combination to presurize the cabin enough to produce bubbles in a soapy solution applied to the outside of the coach.
Would this not be a fairly simple way to test for the adhesion problems or does the loss of adhesion not usually cause water and air infiltration?
I downloaded the pdf and if you want it, I can email it to you or you can go directly to the Prevost site for service publications. It is in the maintenance info section for the H3 VIP 1997 year. Apparently, they have a video cassette demo of this as well.
SUBJECT: WATER INFILTRATION IN H SERIES VEHICLES
Hope it helps.